A previously known railway wagon having the features defined by way of introduction is disclosed in the publication WO 96/11829.
When the load carrier is released from the bogie at one or both ends to be displaced to a loading and unloading position, a supporting device is driven down right between the railway rails to abut against the base. The supporting device comprises a driving wheel, which performs the displacement, and two supporting wheels, which give improved stability to the load carrier during the displacement. For the rails not to be in the way, a concrete platform is arranged between and beside the rails. The upper side of the platform is flush with the upper sides of the rails. A problem with this construction of the supporting device is that it requires a solid and substantially flat base in order to function in a satisfactory manner. Therefore, the above-mentioned, specially built concrete platforms are necessary, on which the supporting device can roll.
It is conceivable that a variant according to WO 96/11829 with four wheels, on which a drive transport band of reinforced rubber runs, could have a wider use, but this is uncertain. Moreover such a construction is relatively complex.
Furthermore EP 0622284 discloses a railway wagon having a load carrier which in turn rests on a subjacent frame structure. The frame structure extends between the bogies and is at its ends fixedly connected to the same. The load carrier is turned about a centre and has on its underside supporting wheels which rest on curved beams of the frame structure. During turning, the wheels roll on these beams. The load carrier is at both ends provided with a rotating supporting wheel on each side which can be lowered in connection with loading and unloading to provide extra safety in the form of protection against tilting. The positioning of the supporting wheels on the sides has the advantage that the above-mentioned special concrete platform is not required. Drawbacks of this railway wagon are on the other hand that the construction only works for turning the load carrier about a centre, that the frame structure is extended in the vertical direction so that the load carrier will be positioned at an undesirably high level above the ground, and that the base must be flat and solid.